Method of Recovering Nickel or Cobalt While Mitigating Corrosion

ABSTRACT

There is provided a method of recovering at least one target metal which is adhered to a stainless steel surface, while mitigating corrosion to the stainless steel surface. The target metal is nickel or cobalt. The method comprises contacting an operative aqueous treatment solution with an operative solid material adhered to a stainless steel surface. The target metal is nickel or cobalt. The operative solid material includes at least one target metal, and at least a fraction of the at least one target metal of the operative solid material is disposed in metallic form. The operative aqueous treatment solution includes soluble treatment material, wherein the soluble treatment material includes nitric acid and copper-comprising material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a filing under 35 U.S.C. 371 of International Application No. PCT/CA2014/000170 filed Mar. 5, 2014, entitled “Method of Recovering Metals While Mitigating Corrosion” which claims priority to Canadian Patent Application No. 2,808,981 filed Mar. 5, 2013, which applications are incorporated by reference herein in their entirety.

FIELD

The present invention relates to processing of metallic materials.

BACKGROUND

Metals such as nickel and/or cobalt are processed to recover the nickel and/or cobalt in purified form. During the processing, in some cases, the metallic nickel and/or cobalt becomes plated to stainless steel surfaces of a container, such as an autoclave, which contains the materials being processed. The plated metal or metals can be recovered by re-dissolution in an aqueous nitric acid solution. Unfortunately, contacting of the aqueous nitric acid solution with the stainless steel surface, while the metallic buildup is present, contributes to accelerated corrosion of the stainless steel surface.

SUMMARY

In one aspect, there is provided a method of recovering at least one target metal which is adhered to a stainless steel surface, while mitigating corrosion (damage) to the stainless steel surface. The target metal is nickel or cobalt. The method comprises contacting an operative aqueous treatment solution with an operative solid material adhered to a stainless steel surface. The target metal is nickel or cobalt. The operative solid material includes at least one target metal, and at least a fraction of the at least one target metal of the operative solid material is disposed in metallic form. The operative aqueous treatment solution includes soluble treatment material, wherein the soluble treatment material includes nitric acid and copper-comprising material.

In another aspect, there is provided a method of recovering at least one target metal from an operative aqueous process solution, wherein the operative aqueous process solution includes at least one target metal-comprising material, such that the operative aqueous process solution includes at least one target metal, wherein the target metal is nickel or cobalt. The method comprises contacting the operative aqueous process solution with reagent material in a reaction zone disposed within a reaction vessel so as to effect production of a reaction product including an operative solid material. The operative solid material includes at least one target metal of the at least one target metal of the operative aqueous solution. At least a fraction of the at least one target metal of the operative solid material is disposed in metallic form. At least a fraction of the produced operative solid material becomes adhered to a stainless steel surface within the reaction vessel. The operative solid material that is adhered to the stainless steel surface is then contacted with an operative aqueous treatment solution. The operative aqueous treatment solution includes treatment material. The treatment material includes nitric acid and copper-comprising material.

In yet another aspect, there is provided a method of recovering at least one target metal from a metalliferrous material, wherein the metalliferrous material includes at least one target metal, wherein the target metal is nickel or cobalt. The method comprises treating the metalliferrous material so as to effect production of an operative aqueous process solution. The operative aqueous process solution includes at least one target metal-comprising material, wherein the at least one target metal-comprising material includes at least one target metal of the metalliferrous material, such that the operative aqueous process solution includes at least one target metal. The treating includes solubilizing at least a fraction of the metalliferrous material. The operative aqueous process solution is then contacted with reagent material within a reaction zone disposed in a reaction vessel so as to effect production of a reaction product including an operative solid material. The operative solid material includes at least one of the at least one target metal of the operative aqueous solution, wherein at least a fraction of the at least one target metal of the operative solid material is disposed in metallic form. At least a fraction of the produced operative solid material becomes adhered to a stainless steel surface within the reaction vessel. The at least a fraction of the operative solid material that has become adhered to the stainless steel surface is then contacted with an operative aqueous treatment solution. The operative aqueous treatment solution includes treatment material, and wherein the treatment material includes nitric acid and copper-comprising material.

DESCRIPTION OF DRAWINGS

The composition of the preferred embodiments of the invention will now be described with the following accompanying drawings:

FIG. 1 is a graphical illustration indicative of the rate of 316L stainless steel corrosion in terms of percentage weight loss of a stainless steel coupon in aqueous nitric acid solution and in the presence of nickel as a function of initial concentration of dissolved copper in the aqueous nitric acid solution;

FIG. 2 is a graphical illustration of the rate of leaching of nickel in an aqueous nitric acid solution as a function of time for various initial concentrations of dissolved copper in aqueous nitric acid solution;

FIG. 3 graphically illustrates the rate of leaching of nickel by an aqueous nitric acid solution including dissolved copper relative to the rate of leaching of nickel by an aqueous nitric acid solution without dissolved copper, for various initial concentrations of dissolved copper, and also illustrates the nitric acid concentration within the aqueous nitric acid solution as a function of time during the leaching of the nickel by the aqueous nitric acid solution; and

FIG. 4 is a graphical illustration of a comparison between: (i) the percentage weight loss of a stainless steel coupon in aqueous nitric acid solution and in the presence of nickel metal as a function of initial concentration of dissolved copper in the aqueous nitric acid solution, and (ii) the percentage weight loss of a stainless steel coupon in aqueous nitric acid solution and in the presence of cobalt metal as a function of initial concentration of dissolved copper in the aqueous nitric acid solution; and

FIG. 5 is a schematic illustration of an embodiment of the reaction vessel within which an embodiment of the method of the present disclosure is being practiced.

DETAILED DESCRIPTION

There is provided a method of effecting recovery of at least one target metal from an operative solid material which is adhered to a stainless steel surface, while mitigating corrosion (damage) of the stainless steel surface.

The method includes contacting operative aqueous treatment solution with operative solid material which is adhered to a stainless steel surface. The operative solid material includes at least one target metal, and at least a fraction of the at least one target metal of the operative solid material is in a metallic form. The target metal is nickel or cobalt. In this respect, the operative solid material includes at least one of metallic nickel and metallic cobalt. The operative aqueous treatment solution includes treatment material. The treatment material includes nitric acid and copper-comprising material. In some embodiments, for example, the copper-comprising material includes an ionic material including cupric ions. In some embodiments, for example, the copper-comprising material is copper nitrate or copper sulphate.

The operative solid material is said to be adhered to the surface when the operative solid material is adhered to the surface or is associated with other solid material which is adhered to the surface.

Stainless steel is any steel alloy with a minimum of 10.5 chromium content by mass.

In some embodiments, for example, the concentration of copper (for example, in the form of cupric ions) in the operative aqueous treatment solution is less than 500 milligrams per litre.

In some embodiments, for example, the concentration of copper (for example, in the form of cupric ions) in the operative aqueous treatment solution is less than 250 milligrams per litre.

In some embodiments, for example, the concentration of copper (for example, in the form of cupric ions) in the operative aqueous treatment solution is greater than 10 milligrams per litre.

In some embodiments, for example, the concentration of copper (for example, in the form of cupric ions) in the operative aqueous treatment solution is greater than 100 milligrams per litre.

In some embodiments, for example, the concentration of nitric acid in the operative aqueous treatment solution is less than or equal to fifteen (15) volume % based of the total volume of the operative aqueous treatment solution.

In some embodiments, for example, the concentration of nitric acid in the operative aqueous treatment solution is less than or equal to ten (10) volume % based of the total volume of the operative aqueous treatment solution.

It is understood that, when an aqueous solution is described herein as “including” material, or material is described as being “in” or “within” an aqueous solution, it is understood that the material is disposed in the aqueous phase.

In some embodiments, for example, the operative solid material includes metallic nickel.

In some embodiments, for example, the operative solid material includes metallic cobalt.

In some embodiments, for example, the operative solid material, which is adhered to a stainless steel surface, is adhered to a stainless steel surface within a container. In some embodiments, for example, the container is a reaction vessel, such as an autoclave.

In some embodiments, for example, the at least one target metal of the operative solid material is derived from an operative aqueous process solution including the at least one target metal. In this respect, in some embodiments, for example, an operative aqueous process solution is provided (for example, supplied to a reaction vessel, or, for example, previously produced by another reactive process within a reaction vessel), including at least one target metal-comprising material, such that the operative aqueous process solution includes at least one target metal. The operative aqueous process solution is contacted with reagent material within a reaction zone 20 disposed in a reaction vessel 10 so as to effect production of a reaction product including the operative solid material (see FIG. 5). The operative solid material includes at least one target metal of the at least one target metal of the operative aqueous process solution. At least a fraction of the produced operative solid material becomes adhered (indicated by reference numeral 40) to a stainless steel surface 30 within the reaction vessel 10.

In some embodiments, for example, after the production of the reaction product has been effected, and prior to the contacting of the operative aqueous treatment solution with the adhered operative solid material, at least a fraction (for example, the entirety, or the substantial entirety) of material within the reaction zone 20 is discharged from the reaction zone 20. In some embodiments, for example, the material is discharged from the reaction vessel 10. After the product material has been discharged from the reaction vessel 10, the operative aqueous treatment solution is contacted with the adhered operative solid material fraction 40.

In some embodiments, for example, the stainless steel surface, to which the operative solid material has become adhered to, defines at least a fraction of the perimeter of reaction vessel internal space 50 of the reaction vessel 10. In some of these embodiments, the reaction vessel internal space 50 includes the reaction zone 20, within which the contacting of the operative aqueous process solution and the reagent material is effected, and the stainless steel surface 40, to which the adhered operative solid material fraction becomes adhered to, is disposed in fluid communication with the reaction zone 10.

In some embodiments, for example, the operative aqueous solution includes at least one of nickel diammine sulphate or cobaltous diammine sulphate. In some of these embodiments, for example, the operative aqueous solution includes nickel diammine sulphate and substantially no cobaltous diammine sulphate. In other ones of these embodiments, the operative aqueous solution includes cobaltous diammine sulphate and substantially no nickel diammine sulphate. In some embodiments, for example, the operative aqueous process solution includes 80 g/L to 100 g/L of nickel diammine sulphate and 80 g/L to 100 g/L of cobaltous diammine sulphate. In some of these embodiments, the reagent material includes molecular hydrogen.

With respect to those embodiments where the at least one target metal of the adhered operative solid material is derived from an operative aqueous process solution including the at least one target metal, in some of these embodiments, for example, the at least one target metal of the operative aqueous process solution is derived from a treatment of a metalliferrous material which includes the at least one target metal. In this respect, in some embodiments, for example, a metalliferrous material is provided, and the metalliferrous material includes at least one target metal-comprising material, such that the metalliferrous material includes at least one target metal. The metalliferrous material is treated to effect production of the operative aqueous process solution, wherein the treating includes solubilizing at least a fraction of the metalliferrous material. In some embodiments, for example, the solubilizing of at least a fraction of the metalliferrous material includes leaching of the metalliferrous material. In this respect, a leachate is produced, and the operative aqueous process solution is, or is derived from, the leachate. If derived from the leachate, the leachate is subjected to one or more serial unit operations to effect production of the operative aqueous process solution. The operative aqueous process solution includes at least one of the at least one target metal of the metalliferrous material.

In some embodiments, for example, the nickel of the metalliferrous material is provided as a nickel concentrate, in any one or more of various forms. In some embodiments, for example, the nickel of the metalliferrous material is in the form of nickel hydroxide. In some embodiments, for example, the nickel of the metalliferrous material is in the form of nickel sulphide. In some embodiments, for example, the nickel of the metalliferrous material is in the form of metallic nickel.

In some embodiments, for example, the cobalt of the metalliferrous material is provided as a cobalt concentrate, in any one or more various forms. In some embodiments, for example, the cobalt of the metalliferrous material is in the form of cobalt hydroxide. In some embodiments, for example, the cobalt of the metalliferrous material is in the form of cobalt sulphide. In some embodiments, for example, the cobalt of the metalliferrous material is in the form of metallic cobalt.

In some embodiments, for example, the metalliferrous material is a mixed metal sulphide concentrate including nickel, cobalt, iron, and copper. In some of these embodiments, for example, the mixed metal sulphide concentrate is derived from an ore. In some of these embodiments, for example, the metalliferrous material is conditioned such that any one of several characteristics of the metalliferrous material is modified to improve the suitability of the metalliferrous material for leaching. An exemplary characteristic which could be modified is particle size. Another exemplary characteristic which could be modified is composition. In this respect, in some of these embodiments, for example, the ore is subjected to size-reduction (i.e. an ore which has been subjected to size reduction, such as by comminution), and then subjected to floatation to yield the concentrate. In some embodiments, for example, the metalliferrous material is milled to yield a concentrate. In some of these embodiments, for example, such metalliferrous material, in the form of the concentrate, is then treated, and the treatment includes effecting leaching of the metalliferrous material with an ammoniacal solution, such as a high pressure ammonia leach. In this respect, in some embodiments, for example, the mixed metal sulphide concentrate is contacted with ammonia within a reaction zone (in some of these embodiments, for example, the reaction zone is disposed at a relatively high pressure, such as at a pressure of 725 to 900 kPa) to effect solubilizing of at least a fraction of the mixed metal sulphide concentrate and thereby effect production of a leachate including the at least one target metal. The leachate is then subjected to selective precipitation, recrystallization or solvent extraction, to separate and purify the metals of interest. The purified metals (either cobalt or nickel) are then treated with hydrogen to produce the metals powder.

In some embodiments, for example, the metalliferrous material is laterite. In some of these embodiments, for example, the metalliferrous material is derived from an ore. In some of these embodiments, for example, the treating of the laterite includes effecting an acid leach (such as a high pressure acid leach). In some of these embodiments, for example, the metalliferrous material is conditioned such that any one of several characteristics of the metalliferrous material is modified to improve the suitability of the metalliferrous material for leaching. An exemplary characteristic which could be modified is particle size. Another exemplary characteristic which could be modified is composition. For example, the acid leach is leaching effected by contacting the laterite with sulphuric acid (such as concentrated sulphuric acid). The leaching effects production of a leachate including the at least one target metal. The at least one target metal is then precipitated from the leachate as a sulphide, and the sulphide precipitate is recovered and further processed to effect recovery, independently, of each one of the at least one target metal. Metal sulphides of nickel or cobalt can be leached with either acids or bases in the presence of oxygen. In one process embodiments, an aqueous ammonia solution, in conjunction with air, is used to dissolve the sulphide concentrate. Several separation steps take place which can involve selective precipitation, recrystallization or solvent extraction to separate and purify the metals of interest. The purified metals (either cobalt or nickel) are then treated with hydrogen to produce the metals powder.

Exemplary processes for treating metalliferrous material, in the form of various ores, to effect production of the operative aqueous process solution, and then effecting production of an operative solid material from the operative aqueous process solution, are described in P. D. Cordingley and R. Krentz, “Corefco Refinery—Review of operations”, Proceedings of Nickel and Cobalt 2005—Challenges in Extraction and Production, 2005, pp 407 425 (see also: F. Crundwell et al., “Extractive Metallurgy of Nickel, Cobalt and Platinum Group Metals”, published Sep. 23, 2011, ISBN-10: 0080968090, ISBN-13: 978-0080968094, 1^(st) ed.)

In some embodiments, for example, the operative solid material, which is adhered to a stainless steel surface, is in the form of a solid electroformed metallic deposit which has become adhered to the stainless steel surface through an electrodesposition process (see, for example, Nickel Plating by George Di Bari in the ASM Handbook, Volume 5, Surface Engineering, published by ASM International, Materials Park, OH 44073, 1994, page 201., and also http://nickel.vale.com/products/nickelplating/science/pdf/EcopyElectroformingGuide.pdf).

Further embodiments will now be described in further detail with reference to the following non-limitative examples.

EXAMPLES

Several experiments have been conducted to observe the effect of the presence of nickel or cobalt on the rate of corrosion of stainless steel in an aqueous nitric acid solution environment. The effect of the addition of dissolved copper to the aqueous environment on the rate of corrosion of stainless steel, as well as the rate of nickel dissolution, is also studied.

Test No. 1

A 316L stainless steel coupon (⅛ of an inch thick, 2½ inches long, and ¾ of an inch wide) is provided in an aqueous solution of nitric acid (100 grams per litre of nitric acid) disposed at a temperature of 70 degrees Celsius. After three hours, the coupon was removed and weighed to determine weight loss of the coupon.

Test No. 2

Same experimental procedure as Test No. 1, with the exception that a 70 g sintered nickel briquette was positioned on top of the coupon within the aqueous solution. The rate of nickel dissolution was measured by solution assays and change in coupon weight.

Test Nos. 3, 5, 6, 7 and 11

Same experimental procedure as Test No. 2, with the exception that the aqueous solution included dissolved copper at a concentration of 0.25 grams per litre (Test No. 3), 0.001 grams per litre (Test No. 5), 0.01 grams per litre (Test No. 6), 0.1 grams per litre (Test No. 7), and 0.5 grams per litre (Test No. 11).

Test No. 4

Same experimental procedure as Test No. 1, with the exception that the aqueous solution included dissolved copper at a concentration of 0.25 grams per litre.

Test No. 9

Same experimental procedure as Test No. 1, with the exception that a sample of metallic nickel, which has become plated to a stainless steel surface of a process vessel, is positioned to sit on top of the coupon within the aqueous solution.

Test No. 10

Same experimental procedure as Test No. 9, with the exception that the aqueous solution included dissolved copper at a concentration of 0.25 grams per litre.

Test No. 12

Same experimental procedure as Test No. 1, with the exception that a 40 g sintered cobalt briquette was positioned on top of the coupon within the aqueous solution. The rate of cobalt dissolution was measured by solution assays.

Results

The results for the above-described experiments are summarized in Table 1, provided below.

% weight loss Test Number Nickel Source Copper Added (g/L) of SS Coupon 2 Sintered Briquette 0.000 1.83 5 Sintered Briquette 0.001 1.56 6 Sintered Briquette 0.010 0.86 7 Sintered Briquette 0.100 0.116 3, 8 Sintered Briquette 0.250 0.0059 11  Sintered Briquette 0.500 0.0018 9 Plating 0.000 0.84 10  Plating 0.250 0.0033 1 None 0.000 0.0035 4 None 0.250 0.0007

The results for Tests 3, 5, 6, 7, and 11 are also represented in FIG. 1, in terms of percentage weight loss in the stainless steel coupon in an aqueous nitric acid solution and in the presence of nickel as a function of the amount of dissolved copper in the aqueous solution.

FIG. 2 illustrates the results for Test Nos. 2, 3, 5, 6, 7, and 11, in terms of rate of leaching of the provided nickel as a function of time

FIG. 3 illustrates results for Test Nos. 3 and 11 (copper added), in terms of leach rate of nickel by aqueous nitric acid solution including dissolved copper relative to the leach rate of nickel by aqueous nitric acid solution including no dissolved copper (ie. Test No. 2), as well as in terms of nitric acid concentration in the aqueous nitric acid solution as a function of time during the leaching of the nickel by the aqueous nitric acid solution (Test Nos. 3 and 11).

FIG. 4 illustrates the percentage weight loss of the stainless steel coupon in the presence of the nickel and cobalt briquettes in an aqueous nitric acid solution as a function of the amount of dissolved copper in the aqueous solution for Tests 3, 5, 6, 7, 11, and 12.

Based on the above-described results, the following is observed.

It appears that increasing dissolved copper concentration in the aqueous nitric acid solution reduces the rate of corrosion of the stainless steel in the presence of nickel. The benefits of increasing dissolved copper concentration appear to level off at dissolved copper concentrations above 0.25 grams per litre.

Test No. 1 illustrates minimal corrosion of the stainless steel coupon in an aqueous solution including a nitric acid concentration of 100 grams per litre. Corrosion of stainless steel coupons is reduced for aqueous solutions including a nitric acid concentration of 100 grams per litre when dissolved copper is added to the solution to a concentration of 0.25 grams per litre of dissolved copper (Test No. 4).

Test Nos. 2 and 9 illustrate substantial corrosion of stainless steel coupons (33 millimetres per year) in aqueous solutions including a nitric acid concentration of 100 grams per litre, with the addition of a nickel briquette (Test No. 2) or the addition of nickel plating (Test No. 9). Corrosion of stainless steel coupons becomes reduced with increasing dissolved copper concentration in those aqueous solutions including a nitric acid concentration of 100 grams per litre and also including nickel briquette or nickel plating (down to 0.1 millimetres per year for a concentration of dissolved copper of 0.25 grams per litre).

Nickel dissolution rate is faster when copper is added. For example, the nickel dissolution rate is about a multiple of three times faster when 0.5 grams per litre of dissolved copper is added to the aqueous nitric acid solution, relative to the case where no copper is added (see FIG. 3). The nickel dissolution rates eventually normalize, due to depletion of the nitric acid.

In the above description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one skilled in the art that these specific details are not required in order to practice the present disclosure. Although certain dimensions and materials are described for implementing the disclosed example embodiments, other suitable dimensions and/or materials may be used within the scope of this disclosure. All such modifications and variations, including all suitable current and future changes in technology, are believed to be within the sphere and scope of the present disclosure. All references mentioned are hereby incorporated by reference in their entirety. 

1. A method of effecting recovering at least one target metal from an operative solid material which is adhered to a stainless steel surface, comprising: contacting an operative aqueous treatment solution with an operative solid material coupled to a stainless steel surface, wherein the operative solid material includes at least one target metal, and at least a fraction of the at least one target metal of the operative solid material is disposed in metallic form, wherein the target metal is nickel or cobalt; wherein the operative aqueous treatment solution includes treatment material, and wherein the treatment material includes nitric acid and copper-comprising material
 2. The method as claimed in claim 1; wherein the concentration of copper in the operative aqueous treatment solution is less than 250 milligrams per litre.
 3. The method as claimed in claim wherein the concentration of copper in the operative aqueous treatment solution is greater than 10 milligrams per litre.
 4. The method as claimed in claim 2; wherein the concentration of copper in the operative aqueous treatment solution is greater than 100 milligrams per litre.
 5. The method is claimed in claim 2, wherein the copper is in the form of cupric ions.
 6. The method as claimed in claim 1; wherein the concentration of nitric acid in the operative aqueous treatment solution is less than or equal to 15 volume % based on the total volume of the operative aqueous treatment solution.
 7. The method as claimed in claim 1; wherein the operative solid material includes metallic nickel.
 8. The method as claimed in claim 1; wherein the operative solid material includes metallic cobalt.
 9. A method of recovering at least one target metal from an operative aqueous process solution, wherein the operative aqueous process solution includes at least one target metal-comprising material, such that the operative aqueous process solution includes at least one target metal, wherein the target metal is nickel or cobalt, comprising: contacting the operative aqueous process solution with reagent material in a reaction zone disposed within a reaction vessel so as to effect production of a reaction product including an operative solid material, wherein the operative solid material includes at least one target metal of the at least one target metal of the operative aqueous solution, wherein at least a fraction of the at least one target metal of the operative solid material is disposed in metallic form, wherein at least a fraction of the produced operative solid material becomes adhered to a stainless steel surface within the reaction vessel; and contacting an operative aqueous treatment solution with the operative solid material that is adhered to the stainless steel surface; wherein the operative aqueous treatment solution includes treatment material, and wherein the treatment material includes nitric acid and copper-comprising material.
 10. The method as claimed in claim 9, further comprising; after the production of the reaction product has been effected, and prior to the contacting of the operative aqueous process solution with reagent material, discharging at least a fraction of material disposed within a reaction vessel inner space, wherein the reaction zone is disposed within the reaction vessel inner space.
 11. The method as claimed in claim 10; wherein the stainless steel surface, to which the adhered operative solid material fraction has become adhered to, defines at least a fraction of the perimeter of the reaction vessel internal space.
 12. The method as claimed in claim 9; wherein the stainless steel surface, to which the operative solid material fraction has become adhered to, is disposed in fluid communication with the reaction zone.
 13. The method as claimed in claim 9; wherein the operative aqueous solution includes at least one of nickel diammine sulphate or cobaltous diammine sulphate.
 14. The method as claimed in claim 9; wherein the operative aqueous solution includes nickel diammine sulphate.
 15. The method as claimed in claim 9; wherein the operative aqueous solution includes cobaltous diammine sulphate.
 16. The method as claimed in claim 13; wherein the reagent material includes diatomic hydrogen.
 17. The method as claimed in claim 9; wherein the concentration of copper in the operative aqueous treatment solution is less than 500 milligrams per litre.
 18. The method as claimed in claim 17; wherein the concentration of copper in the operative aqueous treatment solution is greater than 10 milligrams per litre.
 19. The method as claimed in claim 17; wherein the concentration of copper in the operative aqueous treatment solution is greater than 100 milligrams per litre.
 20. The method as claimed in claim 17; wherein the concentration of nitric acid in the operative aqueous treatment solution is less than or equal to 15 volume % based on the total volume or the operative aqueous treatment solution.
 21. The method as claimed in claim 9; wherein the operative solid material includes metallic nickel.
 22. The method as claimed in claim 9; wherein the operative solid material includes metallic cobalt.
 23. A method of recovering at least one target metal from a metalliferrous material, wherein the metalliferrous material includes at least one target metal, wherein the target metal is nickel or cobalt, comprising: treating the metalliferrous material so as to effect production of an operative aqueous process solution, wherein the operative aqueous process solution includes at least one target metal-comprising material, wherein the at least one target metal-comprising material includes at least one target metal of the metalliferrous material, such that the operative aqueous process solution includes at least one target metal, wherein the treating includes solubilizing at least a fraction of the metalliferrous material; contacting the operative aqueous process solution with reagent material within a reaction zone disposed in a reaction vessel so as to effect production of a reaction product including an operative solid material, wherein the operative solid material includes at least one of the at least one target metal of the operative aqueous solution, wherein at least a fraction of the at least one target metal of the operative solid material is disposed in metallic form, wherein at least a fraction of the produced operative solid material becomes adhered to a stainless steel surface within the reaction vessel; contacting an operative aqueous treatment solution with the at least a fraction of the operative solid material that has become adhered to the stainless steel surface; wherein the operative aqueous treatment solution includes treatment material, and wherein the treatment material includes nitric acid and copper-comprising material.
 24. The method as claimed in claim 23, further comprising; after the production of the reaction product has been effected, and prior to the contacting of the operative aqueous process solution with reagent material, discharging at least a fraction of material disposed within the reaction zone.
 25. The method as claimed in claim 24; wherein the stainless steel surface, to which the adhered operative solid material fraction has become adhered to, defines at least a fraction of the perimeter of the reaction vessel internal space.
 26. The method as claimed in claim 23; wherein the stainless steel surface, to which the operative solid material fraction has become adhered to, is disposed in fluid communication with the reaction zone.
 27. The method as claimed in claim 23; wherein the operative aqueous solution includes at least one of nickel diammine sulphate or cobaltous diammine sulphate.
 28. The method as claimed in claim 23; wherein the operative aqueous solution includes nickel diammine sulphate.
 29. The method as claimed in claim 23; wherein the operative aqueous solution includes cobaltous diammine sulphate.
 30. The method as claimed in claim 23; wherein the reagent material includes diatomic hydrogen.
 31. The method as claimed in claim 23; wherein the concentration of copper in the operative aqueous treatment solution is less than 500 milligrams per litre.
 32. The method as claimed in claim 31; wherein the concentration of copper in the operative aqueous treatment solution is greater than 10 milligrams per litre.
 33. The method as claimed in claim 31; wherein the concentration of copper in the operative aqueous treatment solution is greater than 100 milligrams per litre.
 34. The method as claimed in claim 31; wherein the concentration of nitric acid in the operative aqueous treatment solution is less than or equal to 15 volume % based on the total volume or the operative aqueous treatment solution.
 35. The method as claimed in claim 23; wherein the operative solid material includes metallic nickel.
 36. The method as claimed in claim 23; wherein the operative solid material includes metallic cobalt. 